McGahee also has a fracture in the bone in his lower right leg. He will be on crutches for about a month, and doctors have told him not to put any weight on his leg, according to a source. McGahee will not need surgery and he believes he can come back in four to six weeks, even though the team thinks it's a six- to eight-week injury.
Broncos coach John Fox on Monday afternoon confirmed McGahee's ligament tear and that the running back wouldn't need surgery. The team has not put McGahee on the injured reserve list.
"He's a fast healer. We wouldn't want to prolong it that far," Fox said.
He had 55 yards on seven carries along with one catch for 18 yards on Sunday before going down.
By not putting him on injured reserve, the Broncos, at 7-3 and with a three-game lead in the AFC West, could be thinking about a playoff-time return for their leading rusher, who has 731 yards this year and was having one of his best games of the season -- 55 yards on seven carries -- before the injury Sunday.
In the meantime, they must find a fill-in for McGahee, who was more reliable than explosive and spearheaded a 19th-ranked running game that's averaging 105.3 per contest. Unlike last season, when Tim Tebow was at the helm, the running game is more complimentary than integral to an offense now run by Peyton Manning.
"We've all got to step up and do our part," Hillman said. "Anyone can be an option."
McGahee has built his career on adjusting to circumstances.
Back in 2003, he was finishing his college career at Miami and was considered among the very top prospects. But in the Fiesta Bowl, he tore all the ligaments in his left knee. After multiple surgeries, McGahee fell to 23rd in the draft, and even then, he sat out his first NFL season while rehabilitating the knee.
From there, he opened his career with three 1,000-yard seasons over his first four years. He went on to surpass 8,000 yards over a sturdy decade at a position where careers are often cut short. The Broncos are his third NFL team and he is ranked first among active players with 33 100-yard games.
"His leadership. Power running. You talk about a guy who gets you the tough yards. Those are things we're definitely going to miss," cornerback Champ Bailey said. "But there's a good young group behind him."
Information from The Associated Press was used in this report.